text:
"What's our vector, Victor?": What does this mean?
In Airplane there is a famous sequence:
Roger Murdock: Flight 2-0-9'er, you are cleared for take-off.
Captain Oveur: Roger!
Roger Murdock: Huh?
Tower voice: L.A. departure frequency, 123 point 9'er.
Captain Oveur: Roger!
Roger Murdock: Huh?
Victor Basta: Request vector, over.
Captain Oveur: What?
Tower voice: Flight 2-0-9'er cleared for vector 324.
Roger Murdock: We have clearance, Clarence.
Captain Oveur: Roger, Roger. What's our vector, Victor?
Tower voice: Tower's radio clearance, over!
Captain Oveur: That's Clarence Oveur. Over.

Regardless of the silly dialogue, when the captain asks "What's our vector, Victor?" what is he referring to? Does the scene refer to actual issues that one might discuss with air traffic control?

I should have been quicker to answer this one!

It means you are watching a movie

A vector is defined by a direction and magnitude.  In aviation these represent your heading (the direction) and your speed (the magnitude).  However, in normal aviation usage "vector" only refers to the heading and other nomenclature is used to assign/report speeds.
Example:
"Jetlink 1234, Cleveland Center, turn left heading 250 for traffic"
In which case the vector assigned by ATC is 250 degrees, or 20 degrees south of magnetic west.
To answer the question "What is our vector, Victor?", Victor should state the heading they have been assigned to fly from ATC.
An alternative question would be "What is your heading?" and then you would answer with the direction you are currently flying.

A vector refers to a heading given by Air Traffic Control.
If you want to start learning aviation phraseology, there might be better sources out there:

Say again phraseology database
All clear phraseology manual

There is some resemblance of reality but a number of things are mixed up.
Instead of replying with a 'roger', safety critical information is read back. This allows ATC to confirm that the instruction is clearly understood and if necessary they can correct errors.
The scene describes a take-off. In normal life, and assuming this is controlled airspace, the crew will like to know what to do after getting airborne before they start their take-off roll. There is no point in taking off if you are not allowed to fly in the airspace above the airport. That is why the departure clearance (here "vector 324") will be  issued first. Vectors will be given as "heading". Very often the departure clearance is a standard route instead of vectors. (e.g. LEKKO two alpha departure). On large airports, departure clearances are given on a separate frequency to avoid congestion on the ground and tower frequencies.

Departure clearance
Tower: Fiction two zero niner, after departure, turn right heading three two five, climb and maintain six thousand feet.
FIC209: After departure heading three two five, 6000 ft.

Take-off clearance
Tower: Fiction two zero niner, runway 27, cleared for take-off
FIC209: Cleared for take-off runway 27, Fiction two zero niner.

Hand over to departure frequency
Tower: Fiction two zero niner, contact departure one two three decimal niner
FIC209: Departure on one two three decimal niner, Fiction two zero niner.
FIC209: L.A. departure, Fiction two zero niner one thousand climbing six thousand.
Departure: Fiction two zero niner, radar contact, maintain present heading, climb and maintain ten thousand
FIC209: climbing ten thousand,  Fiction two zero niner
Note that, when on the tower frequency, the words "take-off", and "cleared" are only used when the actual take-off clearance is given. This is to avoid (catastrophic) confusion.
Since "After take-off" cannot be used, instead the phrase "after departure" or "when airborne" is used.

Tenerife (PanAm 1736 / KLM 4805) is a good example of what can happen when one crew believes they've been cleared for takeoff, and another (or ATC) believes otherwise. If I'm not mistaken, Tenerife was a major if not outright the reason for the distinction you make in your final paragraph.

@MichaelKjörling that is correct :-)

I'm a little late to this question, but want to add a little for people who aren't familiar with an aircraft heading.
As you said, the dialog is intentionally silly (and not entirely accurate) but most of what they are saying is loosely based on reality.
The short version is that a vector is where an air traffic controller is talking to an aircraft that is visible on radar, they know where they want the aircraft to go, and they assign a direction for them to fly in order to get there.  This gets the aircraft where they want them without the aircraft needing to navigate on their own, and often allows them to take a "shortcut".

The longer version:
A vector as defined in the Pilot Controller Glossary is:

VECTOR - A heading issued to an aircraft to provide
navigational guidance by radar.
(See ICAO term RADAR VECTORING.)

Of course, that leads to:

RADAR VECTORING [ICAO] - Provision of navigational guidance
to aircraft in the form of specific headings, based on the use of
radar.

Which then leads to:

HEADING - ...

Wait a minute...  They don't define it!  Okay, for those people that aren't pilots, a heading is the direction that an aircraft is flying.  They are three digit numbers corresponding to the 360 degrees in a circle wrapped around a compass rose:

While technically a heading is to the nearest single degree, in most cases ATC will only assign headings that are multiples of ten, or on occasion five, degrees.  So, after North, the commonly-assigned headings would be: 005, 010, 015, 020, etc. all the way around until you get to 355 and then 360.  After that it wraps around again.
So if air traffic control wants you to fly North East, they will tell you to fly a heading of 045, South would be 180, and North would be 360 (fun fact, 000 is not a valid heading).
When ATC assigns a heading for a vector, they always have to be cognizant of what happens if the radio in the aircraft fails.  Obviously they wouldn't expect you to fly straight ahead in that direction forever, so they include the end result of the vector in the clearance.  Usually they also include the direction of the turn for those pilots that aren't very good determining directions.  ;-)  For example, they could say:

N1234, Turn left, fly heading 345, radar vectors to Fort Lauderdale International Airport.

In this case, they expect the aircraft to start a left turn, roll out on a heading of 345 and continue to fly straight until they get another clearance.  If the radio failed, they would turn direct to the airport.
Sometimes they want the aircraft to fly a heading until they intercept a published portion of an instrument procedure.  In this case, they would say something like:

N1234, fly heading 045 to intercept <the procedure>

The airplane would then fly the assigned heading until they get to the procedure and then fly the published procedure!

It's only a bit of a stretch to say that the name Victor is part of the joke, also.  A pilot might be given vectors to join a victor airway...

...which they might ask their colleague Otto to do, @WayneConrad. But that's a different one.


text:
What is the meaning of flap detent names (e.g., 10 degrees)?
When I extend my flaps to 10 degrees, what exactly is the 10 degrees measuring?  Is this referring to the angle of the flap blades themselves, the new angle of the wing chord, the change in the new critical angle of attack or something else?

Selecting the first and/or second detent of flap extension may also extend leading edge devices. Also, in addition to 'lowering' the flaps, it may extend them aft of their retracted position.

The "Degrees" of flap deployment generally refers to the deflection from the neutral (0° - flush with the rest of the wing) position of the flaps.
For most GA aircraft this is an actual angular measurement - 10° of flaps corresponds to the flaps lowering 10° from their neutral position, but the degree of travel can also be given as a percentage (0-100%). The aircraft's maintenance manual will specify the actual travel (and specify how it is to be measured), and if specific position detents are provided there will usually be "rigging limits" specified for where each position stop must be & how accurate the control position must be at each stop.

Is it just me, or does this not explain from what part of the flap is this angle measured? I understand that 0° is the neutral flap position, but is it a measurement to the tip of the flaps or some other method that dictates this angle?

@Qantas94Heavy The aircraft's maintenance manual will specify the actual travel (and specify how it is to be measured) though if it's a plain flap and an angular measurement the "where" doesn't really matter - the angle doesn't change, you're just using a different-sized protractor to measure it...

As I understand it, in small aircraft the degrees of flap is unambiguous: it refers to the angle of the flap to the rest of the wing. For larger aircraft with special flaps (slats, leading edge), the degrees measurement is simply a holdover terminology.

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text:
Why the green inside newer turbofan engine nacelles?
What is the purpose of the recent phenomenon of green being seen inside newer turbofan engine nacelles, just to the front of the fan blades?

Because it's better than black-- that wouldn't contrast with the fan blades, and you'd have less light bouncing around in there during visual inspections.

The green part of the fan case is an acoustic liner, used to dampen the engine noise. The liner is used both in the fan case and on the internal walls of the engine nacelle, but this particular segment is a part of the fan case. (please note that the fan case is an integral part of the engine, and is seperate from the nacelle).

Why is it painted green? It doesn't appear to be that way for any functional reason, just like there is no functional reason for the cyan colour of the Ultrafan blades; it's only a matter of looks.
In fact, it doesn't have to be painted green. On CFM56 for instance, the acoustic liner is painted white.

On GEnx, it is painted black, while on Trent XWB it is painted brown/red. So there is no fixed colour of choice for the acoustic liner.
Sources: PW1100: Fan case diagram, Engine image, Engine-on-wing image, Acoustic liner detail ; CFM56: Acoustic panel image.

I suspect modern liners are dyed, not painted. Paint would compromise its function.

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text:
What information an aircraft responder must give to mode S ground receiver
What is the minimum set of information (for ex.: aircraft registration, position, altitude ... and what else) that a transponder in an aircraft must provide after being interrogated by a ground station ? Is this defined somewhere ? Is there information about the airport of departure/arrival ?

Take a look at this: Decoding ADS-B messages.

@RonBeyer, this is pretty much what I was searching for. If you post it as an answer I will accept it

ADS-B messages are not replies to Mode-S interrogations, they are automatic. When interrogated, a Mode-S transponder replies with the data requested by the interrogation defined by the uplink format (UF) message.  Some of that is discussed in the Enhanced Mode-S section of the document @RonBeyer linked. The same data broadcast by ADS-B can be requested by EHS interrogations, but the formats are slightly different and only the data requested is sent.

very helpful @Gerry. So if interrogated for all of the fields a transponder must reply to all of the requests and give all the info ?

A qualified yes. It will take multiple interrogations and replies and not all interrogations result in replies (for many reasons.) Here's a good primer on Mode S Surveillance Principle. The data exchange info starts at slide 16.

From Mode-S.org
An ADS-B message is 112 bits long:

+--------+--------+-----------+--------------------------+---------+
|  DF 5  |  ** 3  |  ICAO 24  |          DATA 56         |  PI 24  |
+--------+--------+-----------+--------------------------+---------+

DF is the downlink format, ICAO is the 24-bit ICAO identifier of the aircraft, DATA is the message being transmitted, and PI is the parity/interrogator ID.
There are a number of different message types available:

The messages transmit things like position, altitude, turns, track, airspeed, roll angle, turn rate, etc. But they do not contain any information about the originating airport or the destination.

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text:
What is the validity of doing 2D airfoil simulation for axisymmetric bodies?
I am currently working on axisymmetric bodies like fuselages/droplets etc. For this, I am interested in the point of flow separation (if there is) and velocity components at a certain point in space.
I know that XFoil is capable of doing this in a short fraction of time/effort compared to CFD for 2D sections.
What is the validity of taking this approach towards axisymmetric bodies?
With this I mean: using the cross section of the axisymmetric body and simulating this 2D cross section in XFoil, or any other 2D airfoil simulation programme.
Or: can I change the software in some way such that it can represent the physics better?

You should edit the title to be more specific (and to transform it in a question as we are on a Q&A website). Maybe "how to determine the point of flow separation?" or "what are the alternative to XFoil to find point of flow separation?"

Edited title and text

Xfoil analyzes airfoils, not wings, and as such does not account for wingtip effects so its results are invalid for bodies of revolution or even low aspect ratio wings.
More generally, you can reference this answer about the derivation of wing lift from airfoil data. It boils down to the fact that aspect ratio has a massive impact on the 3D flow around the wing. For high AR wings the flow at most sections is close to what can be predicted with a 2D method, but this condition does not hold for slender bodies or near wingtips.
To phrase it differently, we can only apply the results from 2D simulations to wings by avoiding 3D effects. In the case of slender bodies, the entire flowfield is impacted by 3D effects.
Since flow separation is dependent on the pressure field around the body, you need to have an accurate idea of the 3D flow to reliably predict separation points.

Yes, I understand that XFoil does not account for 3D effects as wingtip etc. Following your URL, I also understand that this 2D simulation does not compute the correct lift/drag caused by not accounting for this.
What I am, however, interested in is the point of separation and the velocity field surrounding the body. I do not see how these get affected significantly by having a body instead of a 2D cross-section.

I'm glad you found this useful, but if you don't accept this answer just yet you might get some better ones from other time zones.

You can use Xfoil to do this kind of work: you simply scale your axisymmetric thickness form by 2.3 (IIRC). Maybe 2.4 if you are more interested in the transition location on your body of revolution. The reason for the thickness scaling factor is that a body of revolution appears as a much less 'thick' object to the 3D inviscid flow.

Could you please elaborate why the factor should be 2.3 or give some kind of source for it. Thank you


text:
How does cultural difference impinge upon human factors in aviation industry safety?
Safety through understanding of human factors
This question is based on https://aviation.stackexchange.com/questions/27814/ and related to:

How have deep-seated cultural human factors (particularly in east Asia) in the cockpit been successfully managed in the past 20 years?
To what extent have political (race, gender, social class) attitudes been implicated as human factors in the cockpit?

Aviation industry safety has improved as much through better understanding of human factors in the cockpit as it has through advances in science, technology and engineering, to the extent that practitioners in other sectors (from software development to surgery) are interested in how its principles might apply to their own disciplines.
Aviation practices of this kind that aim to manage or mitigate human factors include:

extensive use of checklists
strict rule-following
extensive cross-checking
health-checking
blameless incident analysis
eliminating authority gradients that make it hard for junior crew to question decisions

Aviation practices across different cultures
These practices and the ideas behind them have largely emerged from western social cultures, and largely in the civilian post-WWII industry, and to a certain extent exemplify aspects of western politics and culture.
Examples of incidents related to cultural human factors
There are many stories (and some are no doubt apocryphal) of how cultural human factors have been involved in incidents. In recent years:

steep cultural authority gradients:

a junior first officer reluctant to question an overbearing captain's decisions
a timid first officer who failed to realise his remote and taciturn captain had actually died

attitudes to regulation, and attitudes of family/VIP exceptionalism:

the pilot who allowed a teenaged family member to touch controls in the cockpit
the pilots who ignored ATC advice to divert in fog because the president and other VIPs were anxious to attend a ceremony

How does cultural difference impinge upon human factors in aviation industry safety?
For example:

How well have they worked (adoption, implementation, outcome) in very different cultures?
Has it been particularly hard for them to find acceptance in other cultures (this applies not just to non-western cultures, but also for example to military culture in the west, where levels of authority and hierarchy are very significant)?
Have different approaches been used or tried with better results, in different cultures?

Also, you didn't really reduce the scope of the question. It is still many questions at once and that does not work here.

I have broken the original question into three new and separate questions, covering: cultural difference and how the industry deals with it (this question); how a particular matter has been dealt with in east Asian; and how race/gender/class attitudes as human factors. They are three independent but related questions. This question significantly reduces the scope of the original, removing two-thirds of it. @JanHudec

@Federico I was specifically advised to break up the original question into new and more specific questions.

Thank you for breaking up the question on this very interesting and complex topic. The original was well written but too broad, this one is still broad but I think it is answerable.

Since the question of which this was supposedly an exact duplicate (http://aviation.stackexchange.com/questions/27814) has been deleted, perhaps this can have the duplicate flag removed.

Is this technically human factors?  The human factors that I'm familiar with is about interface design and pilots' limitations (e.g. where to put buttons, physiological phenomena, or whether a pilot understands what's going on).  The examples cited seem to be more about cockpit resource management, aeronatucial decision making, or risk-management.  I suggest the question be reworded to make this clear.

@CodyP I understood human factors to include human-system interactions in a wide sense, that is, including interaction with the environment as a whole rather than just bodily reaction with the physical environment. If that's not correct, what term covers the total of human interactions in the cockpit, including of course interactions with other humans as well as with the the physical and mechanical aspects of the system?

What you are asking looks like a university assignment on Interface design and sociology. It is a very complex area and your question does not suggest a simple answer but here goes:
These cultural factors are covered by Hofstead's theory of Cultural dimensions. Specifically the Cultural factors of Power Distance, Individualism and Uncertainty Avoidance. I have studied Hofstead (and others) and its relation to Interaction Design and Interface Design for a computing degree.
Power Distance (PD). The higher the score then the more likely the culture is to vest  power in an elite and accept that their decisions. The lower the score the more power is devolved and people are more likely to question leaders.
Individualism (IND). The higher the score the the more loose the societal structure. The lower it is then the society tend to collectivism and rigid structure.
Uncertainty Avoidance (UA). The higher the score then the more the society prefers rigid rules and procedures for all events. The lower then the more relaxed the society is to rules unexpected events.
Note that these overlap considerably.
What this means is that cultures with high PD, UA or Low IND are more likely to follow instruction or even crave instruction and rule. Checklists and instructions are more likely to be followed. Cultures with the opposite may be inclined to be a little more relaxed and may be more of a risk to safety due to a laissez-faire attitude to checks.
However a high PD, low IND and high UA may result in a subordinate unquestioningly accepting instruction from the captain despite knowing that the order was wrong even to the point of crashing.
It is a massively complex subject and to get an answer you really need to be specific with scenarios and cultures.
To see the scores for various cultures then go to geert-hofstede.com/countries.html and try some countries

"What you are asking looks like a university assignment on Interface design and sociology" - not at all.

It was not an accusation, just an observation. I suspect most Universities are shutting down for the summer. Had this been posted months ago I may have suspected a homework question.

@AndyW It's not summer in the Southern Hemisphere ;)

Thanks for this answer, which covers two of the factors I'm interested in (authority gradients; resistance to regulation). Do you know whether research from the social sciences has anything relevant to say about any of the others (e.g. health and privacy - certainly an issue in the Germanwings/Andreas Lubitz case, or blameless incident analysis - potentially threatened by the prospect of criminal/civil actions following incidents)?

@Tim... I live in Scotland. You know it is summer here when the rain warms up a few degrees.

Some countries high on the IND scale will resist what they see as intrusion into the privacy of the individual. Those lower will accept it as protecting the collective. This includes medical/psychiatric information.  If you look at countries such as the UK during virus scares such as SARS, some people wore face masks to protect themselves from catching an infection. Japan tends to collectivism and defending the group. As such when they have a cold they will wear a facemask to prevent giving the infection to others. Japan would likely accept what others would see as intrusion into privacy

In addition to the above,you might also enjoy the work of Prof.Batteau, an aviator and anthropologist.
Here is a link to an abstract of his arguing for anthropology's role in aviation safety.
https://trid.trb.org/view.aspx?id=644343
Also Prof. Sydney Dekker has a lot of interesting things to say on culture and safety- an (ex?) 737 pilot turned safety guru. He is behind the Just Culture framework that encourages the kind of Blameless error reporting mentioned above. My favorite of his articles is titled: Let's Get Rid of the Bad Pilots - http://www.skybrary.aero/bookshelf/books/1232.pdf
More of Dr. Dekker's papers can be found here, http://sidneydekker.com/papers/
You may also be interested in a book chapter by Nicklas Dahlström1 and Lex R. Heemstra that discusses aviation safety in a large multi cultural airline. They argue that the diversity actually dissolves differences and that a shared culture of aviation(aviation safety) transcends these differences in the crew well before they reach the airline. It can be found here: https://www.thelibrarybook.net/pdf-emirates-nicklas-dahlstrom.html

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text:
Why does an aircraft as big as the Airbus A400M use turboprops?
Why is it that a plane as big as the C-17 (the A400M is slightly smaller though) use turboprops instead of turbofans? Both aircraft seem to have the same purpose and are both capable of landing at short runways. So why does the A400M have turboprops?
I want to know why two very large planes have different propulsion systems.

Why do you think props are for small planes? Tu-95 uses props and it's bigger and faster than A400M.

This answer needs some background information.
What became the A400M started as the Future Large Aircraft or FLA in 1983. Airbus was worried what to do with their engineers after work on the A320 was completed, and the next projects, soon to be called TA9 and TA11 (TA for Twin Aisle; they would eventually mature into the A330 and A340), were still far, far away. So the idea of a Transall follow-up was dreamed up to keep Airbus busy, and the engines for this plane would help Snecma to fund the development of their next engine after the CFM56. Yes, the FLA started life with four turbofans!
However, the European military did not like to have turbofans on something that should have the shortest field length requirements possible, and especially their desire for the new transport aircraft to backup under its own power made them to demand turboprops. So in the late Eighties the FLA was converted to turboprops. These were to use the core of the M88 engine, so Snecma would be happy with the new configuration.
This project went through many ups and downs in the quarter of a century between its start and the first flight of the A400M, and many of the sometimes ugly details should better never be mentioned …

The phrase about a racehorse designed by a committee comes to mind...

@RalphJ: It's just the French way of doing business, mutually scratching backs and screwing taxpayers …

@PeterKämpf: a rather unjust generalization (besides the fact that the A400M was developed by France, Germany, UK etc... jointly). One only has to look at the Bradley tank to see that things are much worse elsewhere when it comes to "doing business" or developing new things.

@Joze: Believe me, that thing was conceived entirely by the French partners and forced upon all others. Germany wanted to westernize the An-70: That would have cost 1/3rd of the money and resulted in a technically superior plane. Instead, billions were wasted on Leonid Kuchma and his cronies. The better way to support Ukraine would have been to buy their An-70. But the Ukranian industry never got a fair chance. In short: You have no idea what happened, and the truth is much uglier than you will ever imagine.

@PeterKämpf um... what? What does Leonid Kuchma have to do with developing the A400M? What does Ukraine have to do with the development of the A400M? "Entirely by the French partners and forced upon all others" Quote and source please? France even considered leaving altogether to buy the C-130J. No, Germany was the main partner (not by much) and the one that bought the most planes. YOU have no idea what happened.

@Joze: I was there. Why do you think I know so much about both planes? Again, you have no idea. Nice link to the movie on the Bradley, btw.

@PeterKämpf Why should I believe you where there? Do you have a blog post about this? Would you mind answering my questions? I am genuinely interested!! Either way generalizing that all French business is conducted that way is narrow sighted.

Play nice boys. @Joze, the point of reputation points is just that. Herr Kämpf, your intriguing tidbits do beg for sources. A tell-all book? Aviation Week? - they don't pull punches. I get it about not being willing, or able (NDA's, classification, etc), to describe in detail from personal experience here. But damn, dude, you sure got us extremely curious.

Re: the Bradley. A nod to my previous comment about source reference: Here ya go.  The Pentagon's testing office subjecting equipment under development to unrealistic testing. To wit:  "tests where the Bradley would stand, fully loaded and engine running, against overmatches, attacks with U.S. and Russian munitions that would clearly destroy the vehicle.” Tied like a lamb to the altar and smacked with a big weapon designed to kill fully armored main battle tanks, the Bradley—wait for it—blew up."

Point of view, and time, matters. I remember reading the Army did not want the M-1 tank. Lots of criticism - sand! weight! turbojet engine teething pains. Cost! ... I was thinking it was essentially a bail-out for Chrysler Corp at the time. The Marine Loggie colonel for a certain MEF told me they never wanted the M-1. It's a logistical albatros. Give us an M-60 w/ a modern turret.  Today? OMG world class ass-kicker.

Both aircraft seem to have the same purpose

Not entirely.
The RAF see the C17 as a strategic airlifter, the A400 is seen as a tactical airlifter replacing the turboprop C130.
Strategic airlifters are more likely to make longer, higher-altitude journeys. Where jets are more fuel efficient. They are more likely to operate between airports with concrete runways where FOD is less of an issue.
Tactical airlifters are more likely to make shorter, lower-altitude journeys of the sort where turboprops are more efficient. They are more likely to operate between smaller airfields where FOD may be more of an issue.
References:

ThinkDefence
Airbus
RAF

Some random internet website alleges the fuel costs in \$ per Nautical mile are 19.63 for A400 and 88.14 for C17. They don't say for what mission profile. At a minimum, this illustrates that there is some motivation for matching engine types to expected mix of mission types.

The similar sized AN-70 also uses turboprop engines, illustrating that this choice is not unusual for this sized aircraft.

But when it comes to dimensions (size, etc), the two aircraft are very similar. Why is that so?

@MadhavSudarshan: The A400 is really somewhere between a C-130 and C-17 in size and probably represents a compromise solution to varying requirements of multiple NATO member military commands.

@MadhavSudarshan Though similar in size, the C-17 can carry more than twice the payload of the A400M.

Great comparison - I would suggest to add the An-70 as well. The similarities to the A400M are striking.

@Peter: Done. Ukraine's Antonov evidently agree about the similarities.

Cool! The main differences are the T-tail (the military did not want to build new hangars, so the vertical of the A400 had to be shorter than practical) and the outer engine location of the Antonov (the Russians wanted to drop paratroopers from the front doors, and they should not jump into the propellers). I wish I could give you more than only one upvote.

Nothing can replace a C130 :-)

https://www.flickr.com/photos/sirvonrohr/8688465317/

@fooot Payload comes with both volmue and weight. If you transport mails, weight is more and issue than volume, but for military loads, I don't know which one is limitating (and it may change if you transport troups or helicopters)

@RedGrittyBrick - That boneyard pic shows older C-130 variants at the end of their service lives. There are a bunch of B-52s in the boneyard too but the USAF still keeps an operational fleet of them. The C-130J "Super Hercules", along with a number of variants including the AC-130J Ghostrider (seriously, how cool is an airplane with a howitzer mounted in it?) are still in active production, though the Speed Agile stealth transport is on the drawing boards as well.

As RedGrittyBrick showed, the aircraft are certainly similar in external dimensions, with the A400M being a bit smaller than the C-17. However, the differences are in what the aircraft are designed for. The C-17 is designed to carry heavy cargo long distances, while the A400M is designed to carry lighter cargo shorter distances.
The C-17 is powered by 4 turbofan engines which can together produce 160,000 lbf of thrust. The A400M is powered by 4 turboprop engines that can together produce 44,000 shp, which will come out to probably less than 30,000 lbf. Though both types of engines lose power with altitude, the turboprop will also lose more power with speed.
The difference in power corresponds to a difference in the weights of the two aircraft. The C-17 MTOW is 585,000 lb, while the A400M MTOW is 310,852 lb. The max payload weight is similar: 170,900 lb for the C-17, and 81,600 lb for the A400M. The C-17 is about twice as heavy and can carry twice the payload as the A400M. The C-17 also offers a larger cargo area, with 1.5 m extra width and 3.7 m extra length.
Due to the similar size, both aircraft can carry a similar amount of troops. The C-17 carries up to 134 and the A400M carries up to 116. However, the C-17 can only carry 102 paratroops, while the A400M can still accommodate 116. The A400M can also accommodate 66 stretchers, while the C-17 can only accommodate 36. This illustrates that the A400M is designed to carry lighter cargo such as personnel, but the C-17 isn't really more capable.
As RedGrittyBrick also mentioned, this leads to a difference in roles. The powerful turbofans on the C-17 can carry a lot of payload, but they need longer distances to make up for the higher fuel consumption. The C-17 can fly 2,420 nmi with max payload, and the A400M can fly 1,780 nmi. Similarly, the C-17 can fly 5,610 nmi with paratroopers, while the A400M can fly 3,450 nmi with a 20-tonne payload.

Based on Source

The range of the A400 would have been shorter if the French would not had insisted on flying with full tanks from France to central Africa. It really is meant for tactical air transport, whereas the C-17 is for classic strategic transport with some tactical requirements on top.

While the c17 is twice as big as the A400m by payload and range, the primary reason for using turboprops on the latter is for takeoff from short, unimproved airfields rather than aircraft size.
The four 17ft props on the A400m turboprop can move much larger cylinders of air than can the four 6.5ft fans of the c17. This generates much more thrust when static or moving slowly as in takeoff or landing, particularly important on poor fields. The c17's primary role is strategic, or long distance flight. These are conducted at a higher airspeed where the smaller fan is better suited and large props cause excess drag.
Boeing claims the c17 can land on unimproved airfields. The reality is that it is so heavy that one or two passes makes anything but concrete unusable, and there is a significant inspection/repair bill anytime they go agricultural.
Similarly, Airbus claims the A400m has strategic capability, but payload, speed and range make it an inferior choice.

Simple physics means that turboprops, at low speed, give more thrust for a given amount of fuel burnt than due turbofans.
Complex engineering means that building a turboprop aircraft in the 300 ton category, like the C-17, is impractical:  it would need about 120,000 shp, total.  Building the engines is fairly simple--Pratt, GE, and Rolls-Royce all make gas turbine engines that produce 30,000+ shp -- but neither the needed gearbox nor propellers are within current state of the art.  The real answer is not that Airbus was stupid or France corrupt (if you think politics doesn't come into US procurement, I've got some nice oceanfront property in Nebraska), but that the C-17 is too big for turboprops.

Turbo-prop configuration is blowing air over the wings and developing lift as soon as the blades start turning, this does not happen with turbofans.  This means that turbo prop can have much shorter take-off distance than turbo-fan - which has to wait until forward motion of the aircraft develops lift.  Turbo prop engines are lighter and more rugged than turbofan and less likely to ingest foreign material.  The larger and more numerous the blades the slower they can rotate to produce same thrust and this also makes them quieter.

Turbo props are better for lower speeds. The blades are that size because it also has to pulled along at the same speed as passenger aircraft. Turbo fans would ingest too much debris on landing on non prepared air fields.
This thing can fly at 110kts to refuel helicopters and as fast as a passenger aircraft. It's civil registered so it can fly along civilian airways too. Carries more, flys slower, flys faster, higher and longer than any competition. It's also European so if you are European too......be very proud of what Airbus has acheieved.

The C-17 has turbofans yet can operate from low quality fields. Also, I'm not sure what you mean by "it can fly along civilian airways too".


text:
How do flying wings respond to crosswinds?
Is the vertical tail the primary reason for causing landings to be skewed in a crosswind? Please explain the effect of the fuselage, the tail, or other components.
If the vertical stabilizer is the primary reason for crosswind landings, do flying wings with no vertical tails (say, the B-2) experience this issue?

Short answer: The reason for crabbing (skewed flight, as you call it) during an approach in crosswind is to keep the wings level while maintaining sideslip-free flight. Flying wings are not fundamentally different, because they, too, have stability characteristics similar to those of conventional aircraft.
Airplanes want to be flown without sideslip. Flying in a sideslip (where a component of the airspeed comes from one side) incurs lots of complications:

Some of the lift is also pointing sideways, so the airplane drifts sideways.
Weathervane stability will make the aircraft yaw into the wind. This comes mainly from the vertical tail, but is only one of many components to make the aircraft controllable.
The dihedral effect will cause a rolling moment, lifting the windward wing.
Wing sweep will increase this rolling moment and add more yawing moment.
Since the vertical tail sits upward of the line of symmetry in most airplanes, this also adds to the rolling moment.

Most of these effects are desired, because they make the aircraft easier to fly, but during approach they make it harder to line it up with the runway. If the fuselage is held parallel to the runway, the windward wing needs to be lowered, so some of the lift points sideways into the wind, compensating the side force caused by sideslipping. This is achieved by keeping the ailerons deflected to work against the aforementioned effects, and the rudder needs to keep the airplane from turning into the wind. This is no problem as long as the airplane is high enough. On touchdown, however, such an attitude cannot be maintained, or the aircraft will hit the ground with a part of the wing or an engine nacelle first.
Only by pointing the fuselage into the wind can the course of the airplane be aligned with the runway in a sideslip-free way. This is called crabbing, because when seen from the ground the aircraft's speed has a lateral component, a little like a crab wich is also known for its sideways movement. Now the wings are level, so the touchdown will happen with the wheels first. Unfortunately, now the wheels' rotation direction is not aligned with the runway, and to reduce wear, pilots kick the rudder just before touching the ground to re-orient the aircraft parallel to the runway.
The Lockheed C-5 and the B-52 can rotate their gear struts, which enables both aircraft to touch down in crabbed flight. All other types produce more tire smoke and jerk the aircraft sideways if they touch down this way.

Small aircraft must be landed in cross-wind either in side-slip or decrabbed before touch-down, otherwise they would tip or ground-loop.

My one concern about this otherwise very good answer is that it makes it sound like flying in a slip is somewhat abnormal. It is not considered abnormal flight, and pilots are expected to maintain proficiency.

@rbp: That depends. If sideslipping means you touch the ground first with a wing, sideslipping IS abnormal. My point is that much effort goes into a design to make it fly straight, and the pilot needs to force it into sideslipping. By itself, this is just as normal as flying upside down, but should be avoided in situations like the one discussed here: During landing.

Good answer! But it still does not clear my doubt about the effect of this on tailless aircraft. Except for maybe the point of sweep-induces-rolling-moment,say, a B-2 shall never face the issue of crabbed landing, right?
+1 for the B-52 gear strut rotation fact! :)

Does a B-2 have a dihedral?

@Raj: No, but wing sweep. That works well enough. The B-2 will turn into the wind almost as well as regular aircraft, but this effect varies with lift coefficient. Fast and low flight will reduce directional stability considerably. That's why it uses split ailerons, they add a stability component that increases with speed.

@PeterKämpf You'll find information on flying in a slip in Section 4 "Normal Procedures" in a POH (not in Section 3, "Emergency Procedures")

The vertical tail is NOT the reason for "skewing" (I assume you mean crabbing) in crosswind landings. The answer is directional stability. But first, let's take a look at why crosswind landings are a problem.
Aircrafts fly relative to the air
Aircrafts fly in the air. They fly in a way such that the air pressure is balanced around the aircraft. Thus, if there is a 100 knot perfectly steady wind, any aircraft would fly just fine. A ground observer would see a 100 knot difference in the aircraft's velocity vector, but the relative movement between the aircraft and its surrounding air is exactly the same as a no-wind condition.
Try moving around a train. The train is travelling at 50 mph, yet you can move around the cabin just like on the ground.
Now if some pilot is going to land, he must transition from travelling through air to travelling on the ground. That's when the problem arises. His ground track must be along the centerline of the runway, and he must be pointing in the same direction as his ground track as well.
Back to the train analogy, try jumping from a 50 mph train to the ground. It's difficult because you have to match the 2 movements: one relative to the train and another relative to the ground.
Now we understand that aircrafts move through steady wind just as they do in still air. If a crosswind is 20 knots from the right, the B2 would be drifting to the left at 20 knots if its heading is exactly the same as the runway.
Directional stability
Let's assume what you said is true: on a B2 (which has no vertical tail), the aircraft is not affected by crosswind, and thus can land by pointing the nose straight at the runway.
Then it logically follows, that a crosswind of any magnitude would have an neglectable effect on the aircraft. Which also means, if the aircraft starts floating left or right, there is no way the pilot can control it! He can hold winds level and a constant heading (say 360), but the aircraft may drift sideways!

the B2 is affected by crosswind just not in the same way as a plane with a vertical stabilizer would be.

@ratchetfreak - a plane has no idea whether it is flying through still air or not. Any steady crosswind appears transparent to any aircraft. If you're talking about a sudden change in crosswind, those are gust, and it's not what the OP is asking.

Last para : the crosswind will push the fuselage around! Also, if the aircraft begins to drift, the pilot has access to control surfaces to yaw or give directional forces.
First line : Why is the vertical tail not a reason for crabbing in crosswinds? It will give the aircraft all of rolling, yawing and side force.

Last paragraph: the crosswind will not push the aircraft around because the aircraft has zero response along that axis. If it does, then the assumption (nose pointing straight at runway) will not stand.
The reason is directional stability, not the vertical tail. The vertical tail is only one of many ways to achieve directional stability.

@Raj: the pilot has access to control surfaces to yaw or give directional forces is the answer to: Why is the vertical tail not a reason for crabbing in crosswinds. Basically, it is the reason - the vertical tail (specifically the rudder) is the control surface that yaws the aircraft correcting for the drift. So it is the cause but it is only the cause because the pilot made it do it. If the pilot doesn't deflect the rudder on the vertical tail then the plane would not crab and will only drift further from the runway.

For unaccelerated flight, an aircraft can fly in wings-level zero-sideslip (assuming symmetrical drag/thrust such as asymmetric stores or engine failure) or steady heading sideslip (SHSS). To induce SHSS, the pilot would apply rudder, which in-turn causes sidesplip (Beta). At this point the behaviour of the aircraft is determined by it's inherent aerodynamics as not all behave the same. Just looking at the B2, you will observe that it isn't as 'slab sided' as most commercial or military aircraft might be. Hence there would be less SIDEFORCE than normal aircraft configurations, especially given there is no vertical tail. The effect of this reduction in sideforce means that less angle of bank (lift vector used to counter the sideforce) is required to maintain the SHSS. Now modification of other aircraft configurations such as dihedral and sweep will determine the amount of control that is required to maintain a given SHSS, but doesn't affect the AoB(read sideforce) required due to sideslip.
So the objective in crosswind is to land within the landing gear side load limits. We need to align the aircraft longitudinal axis as close as possible to the runway direction, but we also must have minimal sideways(lateral) velocity.
On a typical crosswind approach, The aircraft will fly a crabbed profile in a wings-level zero heading sideslip for the majority of the profile as this is the most efficient in terms of drag reduction. How the pilot controls the aircraft close to the flare depends on the geometry, control power and handling qualities of the aircraft. This will also determine its crosswind limits. There are two options, land in a SHSS or kick-off drift (KoD), or a combination of both.
Generally, if geometry is limited (ie large wings, engine pods etc) then you're only option is to kick-off-drift (KoD) while trying to keep the wings and close to level as possible. This would be done at the very last moment as the resultant sideforce created by sideslip will make the aircraft drift laterally away from the runway axes, which if left unchecked, might overcome the structural limits of the gear.
If geometry isn't limited but handling qualities are an issue, then the option to use SHSS (wing down) in the flare may be valid. This manoeuvre can be easier to perform in some cases as it is less dynamic in the late stage of the flare whereupon you might encounter other delayed secondary effects seen in KoD such as roll due to sideslip - swept wing aircraft especially. Coming back to aircraft that have low sideforce due to sideslip, we might expect this manoeuvre to be even easier to perform as only small amounts of side slip are required.
Of course, The handling qualities of the aircraft will depend on how the flight controls are implemented and the stability characteristics of the aircraft. This will determine the best techniques to land the aircraft.


text:
Why do turbofan engines have low pressure compressors?
In my understanding turbofan engines usually have 2 stages of compressors:

one low pressure compressor
followed by a high pressure compressor

But it looks like the high pressure compressor cancels the job done by the low pressure compressor, doesn't it?
What's the point of decreasing pressure in the first compressor if you then increase it in the second compressor?  Why not using only the high pressure compressor?

where did you get the idea that a compressor would decrease the pressure?

It's not unique to turbofans. All things that compress have parts that are slightly lower pressure before the part that's slightly higher pressure. That is because going from atmospheric pressure to high pressure requires the pressure to change. And since there cannot be an infinite pressure difference, the pressure must increase by a bit first then by a lot.

The low pressure compressor does not reduce pressure. It increases it, but operates at a lower pressure than the high pressure compressor.  Some engines also have an intermediate pressure (IP) stage.
https://en.wikipedia.org/wiki/Gas_turbine_engine_compressors
https://www.grc.nasa.gov/www/k-12/airplane/compress.html
Each stage increases the pressure as the air is forced back into the flame tubes.

by less it is not given that the delta_p is lower, it simply works at lower absolute values of pressure (it comes firt, after all), hence the name

@Federico Yes, bad choice of words.  I'll edit.  Thanks.

Early jet engines had only one set of compressor disks which were sitting on the same shaft and spinning at the same speed. More modern designs use two or even three concentric spools, each spinning at its own speed. All spools have several compressor discs at the forward and one or a few turbine discs at the rear end, and allowing them to run at different speeds allows each compressor-turbine combination to run more efficiently. Note that all compressor components increase pressure downstream.
Gas turbines must be able to run efficiently not only at full thrust, but also at intermediate thrust settings. Especially in cases where the airplane is not fully loaded, airlines prefer to reduce thrust somewhat, because this stresses the engine less. Enabling different speeds allows to adapt the engine better to the operating conditions. Adding a spool adds complexity and introduces new failure modes, but the difference in speeds between the components makes obvious how much benefit they bring. In case of the GE-90, the low pressure spool runs at 2261.5 RPM when N1 is 100%, and the high pressure spool runs more than four times faster at 9332 RPM when N2 is 100%.
Rolls-Royce's success in the engine market is largely due to its ability to tailor its Trent engine to the many variants of aircraft which are sold by Boeing and Airbus. This tailoring is done by adapting the low speed components while leaving the core identical between models. By having three components to tinker with while its competitors General Electric and Pratt & Whitney have only two, Rolls-Royce has an advantage in the business of offering tailor-made engines.
Another reason for having two independent rotating assemblies can be found on vertical take-off jets: By spinning the low- and the high-pressure components in different directions, their gyro forces can be greatly reduced. While this is not relevant to regular airplanes, hovering a vertical take-off jet is much simpler when its engine does not add a pitch motion to every yawing motion and vice versa.

Three-spool may be today's best technical compromise between efficiency and complexity. I imagine the best effective engine would have a different rotating speed for each disk, compressor and turbine, but is far too complex to build.


text:
If a passenger steps in for the crew, are they eligible for a reward as in maritime law?
Purely hypothetical question on aviation law.
In maritime salvage if your craft rescues/tows/supplies crew to a stricken vessel then you can claim a reward based on the value of the craft and cargo.
Let's assume that you are flying off somewhere warm for a few weeks in a commercial airliner and hear the call "Is there a pilot on board"... and let's all be honest every pilot has fantasised about it.
If you manage to take control of the aircraft and land it safely, does salvage law apply similar to maritime salvage laws? I cannot find anything online that covers it but it must have happened at some point in history.

I'm voting to close this question as off-topic because it would be better asked on law.se.

@RonBeyer if we closed all the jaw related questions here Faa and all related tags would feel very lonely. This question is about law and aviation.  It belongs here and there.

@Antzi I'm not sure I agree, this is more about the application of maritme law to an aviation incident. Substitute the word "aircraft" for "greyhound bus" and I'm not sure I see much difference.

When you are on-board, ship or plane, if you can help to save your life, then you just do it, you don't need an incentive for that. The incentive is for another ship to come and help, in spite of the cost, and the dangers to do so. This is not possible with planes, unless you manage to get on-board while in flight, but in that case the plane is likely a prop in an Hollywood studio. That said, an airlines may (and will) be generous with a passenger who help in a critical situation, but that's not because of the law and they won't thank you by giving you the content of the cargo holds.

The short answer is no but it really depends on what kind of "pilot" is on board.

"Is there a pilot on board"

If the pilot in question is a Private Pilot as per FAA licensing (although its often similar elsewhere in the world). They would be legally prevented from receiving compensation for flight time as per the FAR's.

§ 61.113 Private pilot privileges and limitations:
(a) Except as provided in paragraphs (b) through (h) of this section,
  no person who holds a private pilot certificate may act as pilot in
  command of an aircraft that is carrying passengers or property for
  compensation or hire; nor may that person, for compensation or hire,
  act as pilot in command of an aircraft...

If the pilot in question was a commercial rated pilot they could in theory receive compensation for the flight time but as far as I know there is no aviation law like the maritime law.
Furthermore maritime law generally allows you a portion or all of the recovered cargo value (think treasure salvage) in the case of a hull loss. Here in the US if an aircraft were to go down be it over land or water it becomes an accident scene which the NTSB would have jurisdiction over and is generally in charge of finding and salvaging for their investigation. If you were to recover a piece of an aircraft that was part of an ongoing investigation you may be required to turn it over to the authorities.
The closest scenario that I know of like this, was when a bomber pilot helped land a plane after one of the crew members had an issue. However he was not pilot in command and was only providing support.
All things considered you will probably get a book deal out of the whole thing if it were to happen...

Well, if this were to happen, at the time of the flight they were not "carrying passengers or property for compensation or hire" since they were not actually being paid to do it and were not expecting any compensation for it.  I find it very difficult to believe that a one time reward, after the fact, in extraordinary circumstances would create a problem.  However, if you really want to stretch it you could say that they were trying to help just to create "good will" with the company (maybe they will get a job in the future) and that in itself is compensation....

There is a young fed in some FSDO looking to make a name for him/herself and I bet they'd jump at the chance to be the FAA agent to bust that poor private pilot and fine the airline for any show of gratitude, however small.

Rather than recompense him for his actions they could simply compensate him handsomely for the non-provision of their full service with added compensation for the trauma of having to save their own life.

@acpilot That could happen with just about anything, but would it hold up in court?  I agree with you though (and the last sentence of my comment takes it a bit to that same extreme, lol).

It's administrative law. It won't go to court. The pilot or airline will have to sue to have the penalties recinded. The penalties remain in effect until an administrative law judge (not "regular" court) does away with them. Could take months or years, if ever.


text:
How large are the pilot rest areas of the A380 and B747-8?
How large are the pilot rest areas of an Airbus A380 and Boeing 747-8? What entertainment systems are found in them?

The pilot crew rest areas are not as large as flight attendant rest areas as they only provide space for 2 occupants. A380 and B747-800 pilot rest areas will have 2 sleeping berths, and most airlines will also have 2 comfortable seats equipped with the same in-flight entertainment as the passengers. This gives the resting pilot the choice to sleep in a bed, or relax in a comfortable chair. Sometimes, instead of a chair in the crew rest area, a regular Business class seat will be blocked for the pilot's use.
Airbus A380
Airbus A380 Pilot Crew Rest Area Video

Boeing 747
The B747-800 Pilot Rest area is behind the flight deck. This photo shows 2 bunks with blue bedding. Crew rest seats may or may not be available depending on the airlines own specifications or requirements.

You can find some footage of the A380 crew cabin here. There appears to be about a dozen or so sleeping berths as well as a bathroom. You can find some pictures here and according to the article.

The aviators also have their own entertainment screen when they’re
  away from the cockpit, and unlike the tight-squeeze crew bunks,
  there’s extra headspace if they’d prefer to sit in bed and read a good
  book.

It does not note if the other berths have entertainment systems and its hard to tell in the video. I presume this is something the airline is free to order if they chose to.

Similar footage of the 747 crew cabin can be found here. The video states there are 8 berths. This footage of a united 747 (1:30 in) shows some seats in the crew cabin along with the berths.


text:
Can gliders and single-engine planes have vortices?
I read,

A third physical explanation of the source of induced drag is that the
wing tip vortices contain a certain amount of rotational kinetic energy. This
energy has to come from somewhere; indeed, it is supplied by the aircraft
propulsion system, where extra power has to be added to overcome the
extra increment in drag due to induced drag.

[Source: Introduction to Flight by John D Anderson, Sec: 5.3 "Finite Wings"]
And interpreted thus,

Vortices have rotational energy which comes from propulsion. This additional requirement of "Thrust" can be balanced with Induced drag.

And this makes me question, how gliders form vortices when it does not have engines? Or even single mounted engines in prop planes that do not have engines on wings?
Could you see the vortices created by the glide of owl in the video here and here?
Also, if the phenomena of vortex is not due to engines than why there are four vortices in this famous image:

Where did you read this? Your question is full of misconceptions and this quote is misleading at best.

Tempted to +1 just for that owl video. Consider adding a source for your opening quote, if you have one. It may not be entirely correct though. You might consider adding a sentence immediately after the quote, "Is this quote correct"?

@quietflyer The video is good, but the commentary is awful and makes me want to mute it.

In the picture of the 4-engined plane, I think you are seeing exhaust contrails, which are basically moisture from the (turbulent) exhaust condensing in the cold air at altitude: https://en.wikipedia.org/wiki/Contrail  They're not the same as wingtip vortices.

Vortices have rotational energy which comes from propulsion. This
additional requirement of "Thrust" can be balanced with Induced drag.

The "vortices" in question are generated by the wings themselves, not the propulsion system.  There's a whole "downwash system" in the air behind the wings, which includes the vortices coming off the wingtips themselves.  The sheet of downward-deflected air behind the wings actually gets entrained in the wingtip vortices.
The meaning of the quote is not that the propulsion system directly creates a vortex, but rather that it takes energy to create the wingtip vortices, which (at least in the case of a powered aircraft in horizontal flight) creates a demand for extra power and thrust.  The extra thrust required to create the vortices is exactly equal to the "induced drag", which is the drag associated with creating the vortices, or perhaps more correctly stated, the drag associated with creating the whole downwash system (which includes the wingtip vortices) behind the aircraft.
If something is not entirely technically accurate in my explanation above, I hope another answer will correct it, but that's the general idea that the quote was trying to convey.
The photo you included shows how the contrails behind the engines can help make the wingtip vortices more visible.  The air behind the engines eventually gets entrained in the wingtip vortices.  But you could create a similar picture just by mounting four smoke canisters under the wing of a single-engine airplane, or a glider.  The airliner's engines are not actually creating the two main vortices that we see far behind the aircraft.  Rather, the flow field around the entire wing is.
Hopefully this answer has made it clear that single-engine planes will have wingtip vortices, just as airliners do.
Gliders have wingtip vortices too.  As for where the energy comes to create them, with no motor -- this answer may shed some light on that-- An airplane has an engine that pushes its flight. What force pushes a glider to fly?
In the case of birds, the story is different-- each wingbeat significantly affects the flow field around the entire wing, so there's a closer link between the system of propulsion, and the vortices left behind.

The question has been edited to suggest that the passage I've quoted is actually the question-asker's interpretation of a passage from a textbook.  I'll just let my answer stand as is; I think it is still of some value to the asker of the question.

A simple way to understand where the vortex comes from is Joukowski airfoil theory. The flow pattern around a wing producing lift can be considered as the sum of steady flow (which does not produce any lift) and circulation around the wing (which creates lift and is analogous to the Magnus effect). The circulating flow is left behind as a vortex shed from the wing tip.

The aerodynamics can be explained, something I cannot do for that quote. Let's address the quote story first and, once that's out of the way, let's have a look at the aerodynamics.
Wonky Quote
Vortices rotate, so they have rotational energy. That has noting to do with propulsion. Hurricanes, Tornadoes, ...  are vortices, even pulling the plug in average Joe's bathtub and letting the water circle is a vortex and hence contains rotational energy. No propulsion there. (The rotational energy comes from other sources).
Thrust is not an "additional requirement". It's just that in stationary, horizontal, and level flight, thrust and drag are at equilibrium. But that's total drag, the induced drag is just a part of that.
Bottom line, I cannot support that quote.
Aerodynamics
Induced drag (slightly oversimplified) is just the tip circulation of the wing. Basically, under the wing the aircraft needs higher pressure than above, that's what is creating the lift. But as a parasitic effect, that means that during flight, there is also some air flowing around the wing tip - basically pushed from the high pressure domain below the wing to the low pressure domain above the wing. So around the wing tip, strong vortices are induced. Now, for each meter that the aircraft flies, one meter of vortex is added on either side. These vortices contain kinetic energy, and for lack of another source, it had to be provided by the aircraft. Finally, if you consider that it is "energy spent per distance", and the very definition of energy is force*distance, you can divide that energy by the distance and retrieve a force - the induced drag.
That's the case for any wing, glider or jet fighter, propulsion doesn't change that. The point about gliders is only that they provide that energy by losing altitude.
Then there's a bit more theory on that, if you're interested
https://en.wikipedia.org/wiki/Helmholtz%27s_theorems
and also, the vortices aren't necessarily only two simple vortices on either side, rather they are a spacial distribution, described as a vortex field. But that's just to add more precision, not to change the picture.
The Movies
They're all very great, btw
As for what you see on the 747 - it's not 4 vortices, it's four vapor trails, that roll neatly up into the vortices.

Thank you for the corrections.


text:
How could Airbus better tailor the A380 to the modern market?
I understand any company do things that give net profit. But, had not manufacturing newer engines that increase its Endurance and Range saved it from its decline?

Airbus had designed the A380 to carry as many people as possible so that airlines would be able to fly fewer flights. Instead of flying multiple flights between two cities, airlines could save money by flying just one A380 flight and cramming as many passengers into one plane.
What that would've meant, however, was fewer flights and less flexibility for travellers who don't want to rely on just one flight per day. Very few airlines used the model as intended and the A380 came too late as Boeing was already knee-deep in the 787's development by the time the A380 took its first flight.

Source
Though, bigger aircraft need more ground handling times and management. But with the oncoming innovations, it would have been decreased in future.
For example,
The Wheeltug
Video

As the electric power is used, it also reduces required staffs, cuts down time and Taxi fuel too.
And that may help the airlines too increase the number of flights.

The FlexSys Morphing Wing
Video

As the weight of hydraulics are removed here. This can also lead to higher fuel economy.

Hydrogen Fuel Cell Concept
Video1 Video2

It is nice that the Airbus is itself working on this concept for commercial airliners.
And it would had been nice too if it was implemented to A380 later too.

Reducing the wing span by folding wings on ground for smaller airports. (Though mentioned earlier) Improving engines for shorter Takeoff and Noise Reduction, etc. could help the airliners to reach more destinations with A380.
I want to know the practical feasibilty of introducing an A380neo. And how my above mentioned innoventions fail to be implied in A380? Also, could idling the outer engines thrust help in reducing the wake while landing or gliding, that eventually reduce the safety regulations and requrements for a "Super" aircraft (by this, I meant, will it lead to decrease the seperation required specially for Bigger Aircrafts)?

Nice question, but too broad. Better to ask several questions

I strongly suspect this is opinion-based, no matter how many questions it gets split into.

The A380 has achieved its goal: It won the peeing contest between Boeing and Airbus management for the biggest plane. Having suffered 20 years of Boeing subsidising its smaller jets with the monopoly profits from the 747, Airbus was desperate to break that monopoly. Unintentionally in a Phyrric way, however.

None of the issues these proposals attempt to fix are the main issue with the 380. It doesn't fly to smaller airports not because its wingspan is too big, but because the demand is not there. No smaller airport will generate enough passengers to fill 500 seats at once. Same for ground turnaround times, the reason you won't see a 380 shuttle flight every two hours is not that it takes too long to give it a pushback, but that no airport pair generates the many thousands of passengers per day to fill it.

I disagree with this being opinion based. And not just because I answered it. My answer shows, that this Q can be answered factually. If Q get reopened, I'll gladly edit sources and citations to my answer to beef it up.

Plain and simple, to meet current market requirements, Airbus can do pretty much nothing to make the 380 more "current".
The technical improvements suggested do nothing to change the fact that the 380 is too big, that is, it has too many seats, thus not allowing enough flexibility in this market situation.
In addition to not addressing the main problem, they would need major re-design, except for the wheeltug, which on the other hand is questionable in it's economics: save 20 minutes on ground, haul extra weight for thousands of miles...
There is no sense in technologically further developing a model that has a major "flaw" in it's economics. There are no customers, or not enough at least, for 380neo.
PS: markets are fluid. It may very well be that in furure super jumbos are coming back, but at the moment it does not look like that. If SJ make a comeback, it'll prolly be with a clean sheet design.
PPS: idling outer engines does pretty much nothing for wake turbulence. Wake is "caused" by wings, not engines.

Good answer! Doesn't really look much like a matter of opinion to me.


text:
Why does the optimum cruise altitude depend on the weight of the airplane?
In this answer, Bianfable notes:

[O]ptimum cruise altitude for a 777-200LR at a weight of 340 t is only FL285, but after burning 100 t of fuel it has increased to FL360

Why is that?  Is it simply the momentum of the heavier plane is able to reduce the effect of drag?  Is it linear, or stepped?  And, does the plane rise at some point to the higher level (assuming on a long trip)?
FreeMan suggests in comments it may be the Angle of Attack (AoA) that makes a difference - higher AoA for heavier planes means more drag, so better off at higher altitudes.
As ymb1 notes in comments, from their earlier question, I wonder about this sentence:

At higher altitude the friction and pressure drag is lower but the induced drag is higher, so increasing the mass will cause a much higher jump in drag.

That makes me wonder if it's more related to the different components of drag, than the AoA (or just the AoA, maybe it's a combination of both?)

I looked at this question and its linked questions; I don't think any of them answer this, but it's well possible I misunderstand something here, so please point me to the right one if I missed the duplicate.  Thanks!

IIRC (and I'm not sure of all the specifics), the heavier the plane, the higher the AoA is going to be to maintain level flight at a given altitude. If the plane is 340t at FL360, the AoA is going to be so high that it will be very inefficient (too much drag) which will reduce range. At FL285 and 340t, though, AoA will be sufficiently low to be at max efficiency in cruise.

In case someone asks, my source for that claim is the Boeing 777 FCOM vol. 1 (PI.31.1 Performance Inflight - All Engine). Here is a screenshot of the relevant table.

@ymb1 It probably is too technical; but it seems like that, and a linked question from there, suggest FreeMan's supposition is correct... not sure how to edit the question to match that without suggesting an answer (That I'm not sure of, but certainly it seems reasonable) in the question?

But, from this question, the main answer says "Friction drag is not affected by AoA change" - this is where the 'too technical' comes in, as It's unclear to me if this is disagreeing with the AoA hypothesis, or if "friction drag" is only a component of total drag.

The lift equation:

Lift = wing area x Coefficient of Lift x air density x V$^2$

provides three variables to lift a given amount of weight:  Angle of Attack, air density, and velocity.
Aircraft have the least amount of drag per unit lift at a specific AoA, so best to keep it there.  Speeding up a little is a very good idea but there are 2 factors with the 777, drag from Mach effect (important at high subsonic speeds) and the ability to produce additional thrust in the thin air.  So that leaves altitude (air density) as the best controlling factor for lift production.
Even though the indicated airspeed will be higher for the same True airspeed at FL285 compared with FL360, there is plenty of oxygen for the engines to push the plane along at its optimal AoA and matching airspeed.

True airspeed determines Mach effect

As fuel is burned off, less weight allows the plane to climb to a higher altitude because lower indicated airspeed is required, therefor less thrust, allowing the airliner to stay in its safe Mach "envelope".

does the momentum of the plane reduce the effect of drag?

No, more weight indirectly increases drag. The plane must fly faster, at a higher AoA, or in thicker air to generate the same amount of lift.  All require more thrust, because there is more drag.

Airliners also increase wing area and Lift Coefficient with slats and flaps for lower speed takeoff and landing.

@ymb1 that is correct and edited, thanks.

Because the density of the air decreases with increasing altitude. Thus to achieve the same net lift, to reach equilibrium with a given weight, the wing must have a higher angle of attack.
The higher angle of attack also increases drag which requires additional thrust to overcome.
Thrust available also decreases with increasing altitude due to decreasing air density.  Thus for a given weight a given wing and given engines an optimum altitude is reached which provides some safety margins and optimizes fuel burn.

By "net lift," do you mean lift - weight?


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How have deep-seated cultural human factors (particularly in east Asia) in the cockpit been successfully managed in the past 20 years?
This question is based on https://aviation.stackexchange.com/questions/27814/ and related to:

How does cultural difference impinge upon human factors in aviation industry safety?
To what extent have political (race, gender, social class) attitudes been implicated as human factors in the cockpit?

Successful management of cultural human factors
East Asian airlines used to have poor safety records, notably KAL and Chinese airlines, in part because of cultural human factors in the cockpit (hence the disquiet in Korea over the notorious nut rage incident in 2014).
The last two decades have seen considerable improvements in these safety records.
To the extent that the improvements have been related to better management of human factors (rather than say better technical resources and practices) what approaches have been successful in managing these cultural factors to improve safety (and to what extent)?

"East Asian airlines used to have poor safety records", really?

It seems unlikely to me that anyone here will be able to answer this question authoritatively and objectively.

Related: Worst geographical regions.

@mins yes, for example, Korean Air had many fatal crashes before improving their safety record in recent years.

Yes, you're right, even if we exclude criminal acts.

@mins In the case of Korea, there is a strong feeling that its progress is put at risk by the "chaebols" (wealthy family elites), whose privileged position allows them to undermine the safe regulation and good practices that have improved many of its industries (not just aviation). The "nut rage" incident was felt by many in Korea to be a dangerous step backwards from some hard-won changes. To what extent have safety-improving changes achieved by KAL been an example of cultural management? How were they achieved? By whom?

I believe this question would be clearer if it asked about cultural factors in decision making instead of cultural human factors.  In my opinion the term human factors brings to mind interface design, physiological questions, and pilot cognition/understanding, none of which are mentioned in the question or the current answers.  The question should be reworded to reference safety, CRM, and/or aeronautical decision making instead of just "human factors".

It's not clear how the nut rage incident is related here.  What goes on in the cockpit is an entirely different environment with different rules than the passenger to flight attendant relations.  Perhaps you could clarify what the implications of this incident are for crew resource management?

@CodyP The nut rage case represented an interference with the pilots' operation of the aircraft; Cho received a one-year prison sentence for obstructing aviation safety. But more important are the attitudes behind it. Koreans were horrified to see such attitudes at work in KAL. Those attitudes are ones that most Koreans considered to be a) inimicable to safety b) threatening to the proper functioning of Korean industry c) a return to the bad old days in which power and privilege could overrule even the most important regulations d) an international embarrassment. See http://tinyurl.com/h4oahcf

The commercial aviation world today emphasizes crew resource management (CRM) as an integral part of flying. The premise of effective CRM lies in the principle that any member of the flight crew, whether it's the captain or the first officer, is able to, and should express honest and valid concerns during the flight without worrying about being marginalized or ignored.
Before I start, I would like to point out that Asian airlines are not the only ones to exhibit poor crew management in the past. KLM 4805 (Tenerife), Eastern 401 (crew gets distracted on approach trying to replace a light bulb), and more recently, Air France 447 serve as some examples.
I think the reason why crew management-related accidents in Asia come under the spotlight much more than others (I still hear Asiana 214 jokes all the time, and it's getting really old...) is the fact that the very nature of East Asian culture counters the basic premise of effective CRM — that regardless of position or status in the cockpit, each crew member has a responsibility and a right to speak up. Instead, everybody has a clear-cut hierarchical position roughly based on age. Therefore, whereas accidents in the West are viewed as one-off mistakes made by individuals in an individual case, accidents in the East are viewed more as a natural consequence of the area's culture.
Now, Asian aviation has changed a lot since the '80s. CRM training is a big thing in the industry (just like how the western world has been doing it) and there has been a giant push in the general culture as a whole to create an environment where everyone is heard with equal weight. Change alright, but the roots of old culture remain despite these recent developments, and this is especially true in the corporate environment (including the cockpit). The give-it-to-me-straight-doc cockpit culture in the East still makes it very hard for the FO to speak up and sort of awkward for the captain to allow other crew members to cooperate, even if he or she is willing to make the most use of the crew body.
So, to wrap up my answer to the question, there have been numerous efforts to improve crew management/human factors in the East, but we haven't quite seen the full effects of such changes. Perhaps when the current generation of pilots go (most of them in their '40s and '50s, who were born before the rapid cultural changes in Asia) and the newer, younger generation sets in might we be able to better gage the true effects of changing culture in Asia.
There is no way to summarize this entire subject in a perfectly objective way and there will be people that disagree with some things I've noted. All my above observations were made as a Korean now living in the US. Hopefully my 2 cents help.


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Is there a clear or particular pattern in the mistake-making that leads to a landing at the wrong airport?
I'm interested in how decisions and mistakes are made in the cockpit.
According to a brief news report about a recent landing at the wrong airport (see also the Aviation Herald report):

Landings at wrong airports by commercial pilots, while unusual, are still more common than many passengers may realize or airlines would like to acknowledge.
An Associated Press search two years ago of government safety data and news reports since the early 1990s found at least 150 flights in which US commercial passenger and cargo planes have either landed at the wrong airport or started to land and realized their mistake in time.
In most cases, the pilots were cleared by controllers to fly based on what they could see rather than relying on automation. Many incidents occurred at night, with pilots reporting they were attracted by the runway lights of the first airport they saw during descent. Some pilots said they disregarded navigation equipment that showed their planes slightly off course because the information didn’t match what they were seeing through their windows – a runway straight ahead.

Is there a clear pattern in the decision-making process that leads to such landings?
For example:

Does the transition from automated or instrument flight to visual flight represent a vulnerable point in cockpit management?
Is this phase of flight (perhaps after a long day) associated with moments of pilot inattention?
Are there issues in the relationship that a flight crew has with navigational equipment that allow it to be 'disregarded' in this way?

I don't know if any of these are actually involved, they're just examples that I'm suggesting because I'd like a deeper answer than "sometimes pilots are inattentive".

10 miles seems like a long distance but from the air even airports 40 miles apart can look very close. In this case a contributing factor is that the two airports have nearly identical runway configurations.

Most such incidents are probably linked with loss of situational awareness. The interesting part, of course, is figuring out what causes this loss of SA.

Related: What is supposed to prevent a commercial crew from flying to the wrong airport?

Makes me wonder why airports don't simply flash a Morse code or something from the airport beacon. Positive visual identification. Won't help in IMC, but the instruments are for that.

One thing that they are doing to help with this problem is that in the last few years they have started showing nearby airports on instrument approach plates to help with situational awareness.

I've been in the cockpit three times in which we realized we were maneuvering to land at the wrong airport in time to avoid so. All three times were at night; all three in VFR conditions, all three with the incorrect runway having the same directional orientation as the correct runway, all three with those runways being separated by just a few miles, and all three being the first time the pilot flying had been into the intended airport.
If I had to characterize the root cause, I would describe it as tunnel vision so to speak, being so focused on what was seen as being where the pilot(s) wanted to go that they failed to take into account that the conditions warranted looking around to ensure that that was where they really wanted to go.
The first and only time I personally almost made the mistake was in the early 1970s ferrying a Grumman American Traveler from the factory in Savannah home to Oregon. Close to midnight, we were under a low but legal ceiling over Mississippi flat land along a Victor airway westbound, navigating by a VOR just beyond our intended airport. The aircraft did not have DME. The airway passed a bit south of our intended airport. It also passed a bit south of another airport 30 or so nautical east of the intended. Both airports had runway lights, both were north-south runways. I contacted the intended airport tower, reported the (wrong) airport in sight, and was given clearance to land. On final I realized that the lights of the town were in the wrong place in relation to the airport, looked on the sectional along the airway, and realized my mistake.
The second time was in the 1980s. I was the captain of a SA-227 Metroliner with a brand new first officer the flying pilot. The intended airport was an uncontrolled field, weather was clear. I called the airport in sight and asked the f.o. if he had it. He replied that he did. We typically made a right-base entry for the runway off our en route course. At the appropriate time, configured to land, he started to turn toward the runway. However, instead of turning right, he started a left turn. I realized that when he had said he had the airport in sight he was looking at the runway ahead and to our left rather the the correct runway ahead and to our right.
Finally, in the late 1990s I was jumpseating on a UPS 757 (as I remember) into Miami. It was around 04:30 or so, still dark, clear weather, no traffic. Neither the captain or the f.o. had been into Miami (or at least so they said later). The captain called the airport in sight and Miami Approach cleared them for the visual. My first clue that something was wrong was when the captain then told the f.o., who was the flying pilot, that he needed to get down, get configured. I figured, correctly, that they had made the mistake many, many others had made. They has mistaken the Opa Locka airport for the Miami Airport. Both have multiple runways, both the same pattern. As politely as I could I asked them if they could see a small smudge of blue neon around 10 miles in front of the nose. They said they could, and I told them that was the Miami Sofitel which was completely outlined at the time in blue neon and was alongside the runway they would be using.
Experience is the teacher, which is why when going into Hunter Army Airfield in Savannah for the first time and at night but in clear weather, when asked if I had the airport in sight, I asked for the ILS.

How much onus would you put on the ATC for not noticing deviations? It sounds like the first two you described were to into untowered fields, so it would probably be less likely for them to notice, but on the UPS flight, had you not corrected them, would you have expected Miami approach to notice they were lining up on Opa Locka instead?

@TomMcW The first two were below en route radar and there was no approach radar (long time ago). In the first instance, when I fessed up to the tower what I had done and that I would get there shortly, he just laughed and said they had that happen every now and then. In the case of the UPS flight, I'm sure Miami Approach would have caught the problem had I not pointed it out.

Don't be SO sure, as airplanes have actually landed at OPF when intending to land at MIA....

There  or a number of reasons why this might happen. Nighttime with its lack of visual cues can make it difficult to identify the correct airport. Another one would be a city with multiple airports clustered closely together, especially if a neighboring airports have runways which parallel each other. Crew exhaustion and fatigue can be another one, especially after a long flight.
This was a textbook example of an airplane landing on runway at the wrong airport. In July 2012, a C-17 cargo aircraft which a departed Bagrim airbase in Afghanistan some 16 hours earlier for MacDill Air Force Base in Tampa Florida landed at nearby Peter O’Knight airport in Tampa  in broad daylight.   The crew was fatigued, both airports lie in close proximity to one another and on similarly shaped land, and both have runways which are parallel to the other

And this is (one of the reasons) why we have relief crews.

@Vikki That's a relief!


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Has research into the aerodynamic properties of non-smooth surfaces suggested any promising directions for future aircraft design?
As you might gather from Can planes benefit from Mitsubishi's Air Lubrication System? I'm interested in what possibilities there are for radically different approaches to aircraft body surfaces.
Aircraft body surfaces appear to be as smooth as possible, but not all things that fly well are smooth:

golf balls are dimpled (see the very interesting discussion of Is a golf ball surface a good idea for wings or fuselage?)
birds are feathered
sharks have placoid scales (yes, I am aware that sharks don't actually fly through the air...)

Has scientific or industry research indicated useful possibilities in new surfaces for aircraft body skins - or maybe alternatives to skins altogether?

You can find a lot of what you want here

Possible duplicate of Is a golf ball surface a good idea for wings or fuselage?

@SMSvonderTann: This link is explicitly mentioned in the question.

@SMSvonderTann That's listed as a possibility, but not as the only one.  This questions covers more ground than that one.

I think boundary layer suction might form the basis of a good answer - several experiments have been done in the past. (Leaving this as a comment as I can't find the references.)

Non-smooth surfaces are already used, particularly in some Military Aircraft. If you've ever run your hand down the fuselage of an FA-18 Hornet you will find the surface is quite rough, much like the skin of a shark. At lower speeds very little is achieved, however at higher speeds small bubbles of air buildup in the indentations of the skin thereby creating an extremely slippery surface.
Take a look
Take a look here too
I'm certain my terminology is not correct, sorry about that. I would have put this all into comment, but I'm not allowed yet.

would you happen to have some references to back up your claims?

Sadly I don't know what the technology is called. However, a few years back I was lucky enough to get on-board an F18 and commented on the roughness of the skin. The squadron leader told me it was similar to shark skin and developed, at speed, extremely good aerodynamics as a result.

I did find this: https://www.flightglobal.com/news/articles/aircraft-paint-suppliers-explore-sharkskin-coating-381646/

thank you. if you manage to find also other sources, you can edit your answer to add them and make a better answer.

And this https://physics.aps.org/story/v17/st6

This is exactly the kind of information I was after, would love to see it written up into a full answer.

Glad I could help. I'm sure other aircraft have this but my only experience has been with the Hornet 20 years ago, there must be more since then.


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Are large jet turbofans so easy to spin?
In this question, in the accepted answer, there is a comment by alephzero that says one can actually rotate a large turbofan's blades with one finger! Is that true, can someone elaborate? As an example, does this apply to my google search for strongest turbofan GE9X too?

@Bianfable Thanks for the input. I am mostly concerned about the easiness/resistance of the blades turning, not security or anything like that, so having to climb is no problem for this question.

I would imagine that it depends on how recently and how well the engine has been lubricated.

When you see planes parked in an airport, notice that the blades are turning with any light wind, which means very small torque is needed to turn them

what a great point @hdrz

The fan is huge.  Torque is force multiplied by the radius at which it acts.  It is trivial to generate a large torque with a small force if you apply it at a large radius (think breaker bar, etc).  Jet engines operate at 10k rpm+, so any friction is deadly - both to performance and to the mechanical components, so we also expect that it should turn with extremely low friction by design.

@MD88Fan Also how long since the engine had been run - a warmer bearing is easier to turn than a cold one.

Yes, large turbofans can be turned by hand without too much force. On smaller aircraft this is regularly done as part of the preflight walkaround. You can see an example in this YouTube video of an A320 walkaround:

Admittedly, the pilot turns the engine with four fingers here, but you can see that not much force is required. Turning it with a single finger would easily be possible.
On a larger aircraft like a Boeing 777 you cannot reach the fan when standing on the ground in front of the engine. Spinning the fan by hand is therefore not usually done during the preflight.
This video shows a GE engineer turning the fan blades of a GE90 (the predecessor of the GE9X) engine by hand:

Again, it is not one finger, but he is not using much force to turn it, so it should be possible with one finger.

Ahh, good ol' Capn Joe!

Supplementary detail: an illustration such as https://en.wikipedia.org/wiki/File:Turbofan_operation.svg shows that in many cases the fan is powered directly by a turbine at the other end of the engine, it's not geared to anything which would provide significant resistance when the engine isn't running. (I suggest not trying to see if the fan can be stopped by hand when the engine is running.)

"I suggest not trying to see if the fan can be stopped by hand when the engine is running." You wouldn't even be able to make the attempt - you'd just be sucked into the engine and turned into a paste with the consistency of chunky salsa. I've seen pictures; they aren't pretty.

Turning the engine with one finger is not necessarily recommended, because the leading edges of the fan blades are quite sharp. But it is possible.
For some experimental vibration measurements, it is preferable to keep the rotors turning slowly to avoid the bearings "sticking" in one position and confusing the results. A common way to do this is simply to put an ordinary office desk fan in front of the engine. That tiny amount of air flow is enough to keep the fan slowly turning.

Some engines have a mechanism to slowly turn the shaft(s) during cool down . I understand there is a risk of the shaft getting a slight deviation from straight if allowed to cool down in one position.

@blacksmith37, different turbine vendors have different cool-down procedures. I'm not a pilot, but have worked with steam and gas turbines a lot. In a cooling steam turbine, the dripping condensation makes the bottom of the turbine much cooler than the top, and the shaft contracts on the bottom, causing the it to bow upwards ("hogging"). This lasts until the temperatures even out. To prevent this, the turbine shaft is slowly rotated when cooling. I haven't seen this procedure on gas turbines; many vendors feel it's not necessary for gas: the temp differentials are much smaller.

If you look at the turbine fan, they often have a spiral painted on the center ; I have often seen them slowly turning.

Yep, I've heard of gas turbines that have a slow rotation requirement or recommendation during cool-down, but I've never worked on one myself. Opinion seems to be divided on whether this is worthwhile.

@blacksmith37 More often than not, the slow turning you'll see on the intake fan of a turbofan jet engine is just the engine windmilling. It doesn't take much wind at all to windmill it. It takes it quite a while to completely stop after it's shutdown, not because anything is driving it to continue spinning slowly, but just because the bearings have to be really good to prevent it from burning up at full power and, thus, there's not much friction from the bearings to stop the rotation once the engine is shut down.